1. Field of the Invention
The present invention relates to semiconductor devices having a so-called SOI (silicon on insulator) structure in which a semiconductor layer is provided on an insulating surface.
2. Description of the Related Art
As an alternative to an integrated circuit using a silicon wafer which is manufactured by thinly slicing a single-crystal semiconductor ingot, an integrated circuit using a semiconductor substrate which is referred to as a silicon on insulator (hereinafter also referred to as “SOI”) in which a thin single-crystal semiconductor layer is provided on an insulating surface has been developed. The integrated circuit using an SOI substrate has attracted attention as a semiconductor integrated circuit which reduces parasitic capacitance between a transistor and the substrate and improves the performance of a semiconductor integrated circuit.
As a method for manufacturing SOI substrates, a hydrogen ion implantation separation method is known (e.g., see Reference 1: Japanese Published Patent Application No. 2000-124092). A hydrogen ion implantation separation method is a method by which hydrogen ions are implanted into a silicon wafer to form a microbubble layer at a predetermined depth from the surface, and the microbubble layer is used as a cleavage plane to bond a thin silicon layer to another silicon wafer. In addition to performing heat treatment for separation of a silicon layer, it is necessary to perform heat treatment in oxidizing atmosphere in order to form an oxide film on the silicon layer, to remove the oxide film, and then to perform heat treatment at from 1000 to 1300° C. to increase bonding strength.
On the other hand, a semiconductor device in which an insulating substrate such as high heat resistance glass is provided with a silicon layer is disclosed (e.g., see Reference 2: Japanese Published Patent Application No. H11-163363). This semiconductor device has a structure in which the entire surface of a crystallized glass having a distortion point of 750° C. or more is protected by an insulating silicon film, and a silicon layer obtained by a hydrogen ion implantation separation method is fixed to the insulating silicon film.